NCP4305LLCGEVB

NCP4305DGEVB NCP4305 Synchronous Rectification Evaluation Board User's Manual www.onsemi.com Table 1. GENERAL PARAMETERS SMPS Type Supply Voltage Reverse Voltage Effective Resistance LLC 5−35 V 40 V 0.9 mW EVAL BOARD USER’S MANUAL Description This evaluation board user’s manual describes a high efficiency synchronous rectification evaluation board that can easily replace a secondary side rectification diode in an SMPS. The NCP4305 is used as synchronous rectification controller. The evaluation board has very few external components and illustrates how small and effective such a design can be. The NCP4305 features a very precise 0 mV turn-off comparator that supports even very low current flowing through the MOSFET even when very low RDSON synchronous MOSFETs is used. Key Features • • • • • • • • • Precise Turn-off Comparator Wide Input Voltage Range High Operation Frequency Strong MOSFET Driver High Efficiency Adjustable Minimum On and Off Times Light Load Detection Feature Capable to Operate in Positive and Negative Branch Small size Figure 1. NCP4305 Evaluation Board © Semiconductor Components Industries, LLC, 2016 January, 2016 − Rev. 1 1 Publication Order Number: EVBUM2350/D NCP4305DGEVB Connection Diagram VCC + + VCC A) B) Figure 2. Possible Connections in to Circuit rectification) to provide power to the evaluation board. VCC should be referenced to A1 or A2 points. When LLD function is used it is needed to connect LLD1 pin with opposite side rectifier cathode. The evaluation board can be connected in circuit where the rectification diode is in the positive or negative branch. When connection to a positive branch is used, it is necessary to use an external power supply (or auxiliary winding with www.onsemi.com 2 NCP4305DGEVB Evaluation Board Schematic MIN_TOFF VCC DRV VCC 2 GND GND CLLD1 NU RLLD1 NU RLLD2 NU DRV MIN_TON 7 4 LLD 10 kW RLLD3 NU GND M2 CSNB 3.9 nF C RTRIG 1 kW TRIG/DIS GND D4 BAS20 CLLD2 NU M1 NVMFS5830 RCS 0W 5 TRIG/DIS NCP4305S08 RLLDD_PD GND 6 CS A1 RG 0W 8 MIN_TOFF GND 3 RMIN_TON 4.7 kW RMIN_TOFF 22 kW RMIN_TOFFM NU A2 RSNB1 15 kW IC1 1 GND RG_PD 10 kW C2 1 mF/35 V RTRIG_PD 1 kW C1 100 nF GND RSNB2 NU GND GND D1 BAS20 LLD1 LLD Figure 3. Schematic of the NCP4305 starts to operate and SR transistor gate voltage is modulated according to skip duty cycle. The second option is for system which transfers lot of energy in few first pulses in skip and then transferred energy is minimal. In this case LLD circuit time constant is low and RLLD3 resistance is close to 0. LLD pin voltage drops down in first switching pulse in skip mode and NCP4305 wakes up fast and allows using fully open SR transistor. When skip burst ends, LLD voltage goes high and if time between skip bursts is long enough NCP4305 enters disable mode to save energy. The evaluation board was designed to support a minimal external component count implementation. C1 and C2 are decoupling capacitors. They should be placed as close as possible to the VCC and GND pins. Resistors RMIN_TON and RMIN_TOFF are used to set the protection interval when the synchronous MOSFET is turned on and off. Resistor RMIN_TOFFM is placed there to support a situation when an external circuit provides control for minimum off-time modulation. This is needed only in situations when the minimum off-time cannot be set across the whole range of power supply operation. Resistor RTRIG_PD is only pull down for TRIG pin and RTRIG is only protection resistor. A position for a gate resistor RG is provided in case there is a need to slow down the MOSFET switching process. The turn-off (and also the turn-on) threshold can be lowed when resistor RCS is used. Components CSNB, RSNB1 and RSNB2 form a snubber circuit. LLD circuit consists of CLLD1, CLLD2, RLLD1, RLLD2, RLLD3 and D4. Purpose of circuit is to estimate output power. This can be done in two ways. The first is to measure duty cycle of skip burst. LLD circuit time constant is high and it filters and averages duty cycle ratio. This is good for systems which transfer low energy during skip each switch cycle. When duty cycle of skip bursts is low NCP4305 enters disable mode to save energy, when it is higher SR controller Circuit Layout The PCB consists of a 2 layer FR4 board with 35 mm copper cladding. All components are surface mount and most of the components that may require adjustment are on the same side and use 1206 values for easy rework. Critical component such as blocking capacitors C1 and C2 have to be placed carefully near the IC. The synchronous driver path to the MOSFETs was done with very low resistance and parasitic inductance to minimize emissions and minimize turn-on and turn-off times. The same is true for the CS pin. For the CS pin, a kelvin contact was done to be able to sense the voltage directly at the drain. Improper connection of the GND and CS connects can impact the turn-off process especially when a very low RDSON MOSFETs are used. www.onsemi.com 3 NCP4305DGEVB Figure 4. Top Layer Figure 5. Bottom Layer Figure 6. Top Side Components www.onsemi.com 4 NCP4305DGEVB Figure 7. Bottom Side Components Figure 8. Evaluation Board Photo − Top Side Figure 9. Evaluation Board Photo − Bottom Side www.onsemi.com 5 NCP4305DGEVB Table 2. BILL OF MATERIALS FOR NCP4305 PUT-IN BOARD SO-8FL (Note 1) Value Tolerance Footprint Manufacturer Manufacturer Part Number Substitution Allowed Ceramic Capacitor 100 nF 10% 1206 Kemet C1206X104K5RACTU Yes Ceramic Capacitor 1 mF/50 V 10% 1206 Kemet C1206X105K5RACTU Yes 2 − NU − 1206 − − Yes CSNB 1 Ceramic Capacitor 3.9 nF − 1206 Kemet C1206C392K5RACTU Yes D1, D4 2 Switching Diode BAS20HT1G − SOD−323 ON Semiconductor BAS20HT1G Yes IC1 1 Secondary Side Synchronous Rectification Controller NCP4305D − SOIC−08 ON Semiconductor NCP4305DDR2G No M1, M2 2 N-Channel Power MOSFET NVMFS5830NL − SO−8FL ON Semiconductor NVMFS5830NLT1G Yes RCS, RG 2 Resistor SMD 0W 5% 1206 Yageo RC1206JR−070RL Yes RG_PD 1 Resistor SMD 10 kW 1% 1206 Yageo RC1206FR−0710KL Yes RLLD_PD, RTRIG, RTRIG_PD 3 Resistor SMD 1 kW 1% 1206 Yageo RC1206FR−071KL Yes RLLD1, RLLD2, RLLD3, RSNB2, RMIN_TOFFML 5 Resistor SMD NU − 1206 − − Yes RMIN_TOFF 1 Resistor SMD 22 kW 1% 1206 Yageo RC1206FR−0722KL Yes RMIN_TON 1 Resistor SMD 4.7 kW 1% 1206 Yageo RC1206FR−074K7L Yes RSNB1 1 Resistor SMD 15 W 1% 1206 Yageo RC1206FR−0715RL Yes Parts Qty Description C1 1 C2 1 CLLD1, CLLD2 1. 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